Autonomous mobile robot

ABSTRACT

Disclosed is a space-saving autonomous mobile robot capable of switching two types of light irradiation appropriately. The robot includes a moving mechanism, an autonomous movement controller for controlling the moving mechanism, a self-location recognition unit for sensing a self-location of the robot, a map data storage unit for storing a map data on locations of marks, a slit light device for irradiating a detection area with slit light, an infrared device for irradiating a detection area with infrared rays, and a switch determination unit for comparing a mark-formed region and the self-location, and then, for switching between the slit light and infrared devices, based on the comparison result. Moreover, the infrared device irradiates the detection area when the self-location is within the mark-formed region, while the slit light device irradiates the detection area when the self-location is outside the mark-formed region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Patent Application2004-361905 filed on Dec., 14, 2004, the disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to autonomous mobile robots, generally.More specifically, the present invention is directed to an autonomousmobile robot equipped with both a road surface sensing device and acurrent location verification device.

2. Description of the Related Art

A typical mobile robot is equipped with a device for checking a roadsurface, which is called “road surface sensing device” This device has afunction of determining whether or not there is any obstacle in front ofthe robot. Specifically, the device irradiates a road surface in frontof the robot with predetermined slit light, and then, captures an imageof the irradiated area. Finally, it analyzes the pattern of the light inthe captured image (see Japanese Unexamined Patent ApplicationPublications 6-43935 and 2002-144278).

In addition, a typical mobile robot is equipped with a device forverifying its current location, which is called “current locationverification device”. This device allows the robot to pick up images oflandmarks formed beforehand on an active area, and it then verifies orrecognizes the current location or the surrounding conditions of therobot, based on features of the captured landmarks, such as a color,size or shape (Japanese Unexamined Patent Application Publication2002-149240).

Generally, a robot, particularly a legged robot is provided with varioussystems such as sensors, circuits and power units. Therefore, it isdifficult for such a robot to have an inner space enough to accommodateboth a road surface sensing device and a current location verificationdevice. If both devices are accommodated, then the robot ends upenlarged.

Moreover, if installed in a robot, then both devices need to be switchedappropriately in order to save the energy. This is because landmarks arenot necessarily formed throughout the active area.

The present invention has been conceived, taking the above descriptioninto account. An object of the present invention is to provide aspace-saving autonomous mobile robot capable of switching two types oflight irradiation, such as infrared rays and slit light, appropriately.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided, anautonomous mobile robot including:

(a1) a moving mechanism;

(a2) an autonomous movement controller for controlling the movingmechanism;

(a3) a self-location recognition unit for sensing a self-location of theautonomous mobile robot within an active area;

(a4) a map data storage unit for storing a map data on locations ofmarks formed on the active area;

(a5) a slit light device for irradiating a detection area with slitlight;

(a6) an infrared device for irradiating a detection area with infraredrays;

(a7) a switch determination unit for comparing a mark-formed regionstored in the map data storage unit and the self-location sensed by theself-location recognition unit, and then, for switching between the slitlight device and the infrared device, based on a result of thecomparison;

(a8) a capture unit for capturing an image of the detection areairradiated by the slit light or infrared rays;

(a9) a road surface sensing unit for detecting conditions of a roadsurface by analyzing the captured image of the detection area beingirradiated with the slit light; and

(a10) a mark sensing unit for detecting marks by analyzing the capturedimage of the detection area being irradiated with the infrared rays. Inaddition, the infrared device irradiates the detection area when theself-location is within the mark-formed region, while the slit lightdevice irradiates the detection area when the self-location is out ofthe mark-formed region.

Moreover, it is preferable that the autonomous mobile robot includes aself-location correction unit for correcting the self-location, based onlocations of the marks detected by the mark sensing unit.

According to another aspect of the present invention, there is provided,a process for controlling an autonomous mobile robot including the stepsof:

(b1) sensing a self-location of the autonomous mobile robot within anactive area;

(b2) acquiring a map data on locations of marks formed on the activearea;

(b3) comparing the self-location and a mark-formed region being acquiredfrom the map data; and

(b4) switching between slit light and infrared rays, based on a resultof the comparison, so that a detection area is irradiated. In addition,the slit light and the infrared rays are switched in such a way that thedetection area is irradiated by the infrared rays when the self-locationis within the mark-formed region, while the detection area is irradiatedby the slit light when the self-location is out of the mark-formedregion.

Other aspects, features and advantages of the present invention willbecome apparent upon reading the following specification and claims whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For more complete understanding of the present invention and theadvantages hereof, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings wherein:

FIG. 1A is a view depicting an autonomous mobile robot according to oneembodiment of the present invention, which irradiates a detection areawith slit light;

FIG. 1B is a view depicting the autonomous mobile robot which irradiatesa mark-formed region with infrared rays;

FIG. 2 is a block diagram of a configuration of the autonomous mobilerobot;

FIG. 3 is a perspective view depicting a body of the autonomous mobilerobot;

FIG. 4 is a block diagram of a surrounding area sensor of the autonomousmobile robot; and

FIG. 5 is a flow chart for a process in which the autonomous mobilerobot switches between slit light irradiation and infrared irradiation.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE INVENTION

A detailed description will be given below, of an autonomous mobilerobot according to an embodiment of the present invention, withreference to accompanying drawings. In the following description, thesame reference numerals are given to the same parts, and duplicatedescription is therefore omitted.

<Configuration of Autonomous Mobile Robot>

First, an autonomous mobile robot of one embodiment of the presentinvention will be given below, with reference to FIG. 1. Thereinafter,an autonomous mobile robot is just called “robot”, occasionally.

Referring to FIGS. 1A and 1B, a robot R includes a head R1, arms R2,legs R3 and a body R4. The head R1, arms R2 and legs R3 are driven byindividual actuators, and the bipedal movement is controlled by anautonomous movement controller 50 (see FIG. 2). Herein, the legs R3which are called “legged moving mechanism”. The detail of the bipedalmovement is disclosed by Japanese Unexamined Patent ApplicationPublication 2001-62760, etc.

The robot R moves around within an active area such as an office or ahallway in order to execute specific tasks, for example, the delivery ofdocuments. While moving, the robot R checks the road surface of the areaor searches for marks M thereon by irradiating the surface with laserslit light or infrared rays, as shown in FIGS. 1A and 1B. Specifically,the robot R checks its current location, and when being within an activearea, the robot R detects step heights, bumps, dips or obstacles byirradiating the area surface with the laser slit light. Meanwhile, whenbeing within a specific area where marks M are formed, the robot Rdetects the marks M by irradiating the area surface with the infraredrays, thereby verifying or correcting the current location.

The marks M, which are made of an infrared-reflecting material, areformed on the specific areas within the active area, for example, anarea in front of a door. It is preferable that each mark M betransparent or small enough not to worsen the sight of the area. In thisembodiment, three reflecting points make up a single mark M, and twomarks M make a pair, as shown in FIG. 1B. The marks M is related tolocation data, and this data is contained in map data and stored in amap data storage unit.

Next, referring to FIG. 2, the robot R includes the head R1, the armsR2, the legs R3, the body R4 (not shown), the cameras C and C, a speakerS, a microphone MC, an image processor 10, an audio processor 20, acontroller 40, an autonomous movement controller 50, a radiocommunicator 60, and a surrounding area sensor 70. Furthermore, therobot R includes a gyro-sensor SR1 for sensing its orientation, and aGPS (global positioning system) receiver SR2 for recognizing itscoordinates. Herein, the gyro-sensor SR1 and the GPS receiver areincluded in a self-location recognition unit.

[Camera]

The cameras C and C have a function of producing digital images ofobjects, and they may be color CCD (Charge-Coupled Device) cameras. Thecameras C and C are arranged horizontally, and output the producedimages to the image processor 10. The cameras C and C, the speaker S andthe microphone MC are contained in the head R1.

[Image Processor]

The image processor 10 has a function of treating the images receivedfrom the cameras C and C, and it recognizes the presence or absence ofpersons and obstacles around the robot R in order to realize thesurrounding conditions. This image processor 10 is composed of a stereoprocessor 11 a, a moving body extractor 11 b, and a face identifier 11c.

The stereo processor 11 a performs pattern matching by using, as areference, one of the respective two images captured by the cameras Cand C. Following this, the processor 11 a determines the parallaxesbetween the pixels of one image and the corresponding pixels of theother image, thus generating a parallax image. Finally, it outputs theparallax image and the original images to the moving body extractor 11b. Note that the parallax depends on a distance between the robot R anda captured object.

The moving body extractor 11 b takes out one or more moving bodies fromthe captured image, based on the images from the stereo processor 11 a.This action is done to recognize one or more persons, under thecondition that a moving object (or body) is a person. To take out amoving body, the moving body extractor 11 b memorizes several pastframes, and it carries out the pattern matching by comparing the latestframe (or image) and the past frames (or images). As a result, themoving body extractor 11 b determines the moving amounts of the pixels,and produces moving amount images. If the moving body extractor 11 bchecks whether or not there is any pixel with a large moving amount,based on the parallax image and the moving amount image. If the pixelwith a large moving amount is found, then the moving body extractor 11 bdetermines that a person is present within an area at a predetermineddistance away from the cameras C and C. Following this, the moving bodyextractor 11 b outputs the image of the person to the face identifier 11c.

The face identifier 11 c takes out skin-colored portions from the imageof the moving body, and recognizes the position of its face, based onthe size, shape, etc. of the extracted portions. Similarly, the faceidentifier 11 c recognizes the position of the hands. The faceidentifier 11 c outputs data on the recognized face position to thecontroller 40 so that the data is used to move or communicate with theowner of the face. Also, it outputs data on the recognized face positionto the radio communicator 60, as well as to the robot controller 3through a base station

[Audio Processor]

The audio processor 20 is composed of an audio synthesizer 21 a and anaudio identifier 21 b. The audio synthesizer 21 a generates audio datafrom character information stored beforehand, based on a speech actioninstruction determined and outputted by the controller 40. Subsequently,the audio synthesizer 21 a outputs the generated audio data to thespeaker S. Upon generation of the audio data, the relation between thecharacter information and the audio data is used.

The audio identifier 21 b generates the character information from theaudio database on the relation between the audio data (having beeninputted from the microphone MC) and the character information.Subsequently, the audio identifier 21 b outputs the generated characterinformation to the controller 40.

[Autonomous Movement Controller]

The autonomous movement controller 50 is composed of a head controller51 a, an arm controller 51 b, and a leg controller 51 c. The headcontroller 51 a, the arm controller 51 b and the leg controller 51 cdrive the head R1, the arms R2 and the legs R3, respectively, inaccordance with an instruction from the controller 40.

The data sensed by the gyro-sensor SR1 or GPS receiver SR2 is outputtedto the controller 40. The controller 40 uses this data to decide theaction of the robot R, and sends it to a robot controller 3 through theradio communicator 60.

[Radio Communicator]

The radio communicator 60 is a communication device that sends/receivesdata to or from the robot controller 3. The radio communicator 60 iscomposed of a public line communication device 61 a and a wirelesscommunication device 61 b.

The public line communication device 61 a is a wireless communicatorusing a public line such as a portable phone line or a personal handyphone system (PHS) line. Meanwhile, the wireless communication device 61b is a short-distance wireless communicator such as a wireless LAN inaccordance with IEEE802.11b.

The radio communicator 60 selects one among the public linecommunication device 61 a and the wireless communication device 61 b,depending on a connection request from the robot controller 3, therebysending/receiving data to or from the robot controller 3.

[Surrounding Area Sensor]

Referring to FIG. 2, the surrounding area sensor 70 includes a laserdevice 71, a light emitting diode (LED) device 72, infrared cameras 73and 73, and a sensor controller 80. Herein, the laser device 71 and theLED device 72 refer to a slit light device and an infrared device,respectively.

The surrounding area sensor 70 irradiates a detection area with slitlight from the laser device 71 or infrared rays from LED device 72, andit then captures the images of a detection area by using the infraredcameras 73 and 73, thereby sensing the surrounding conditions of therobot R. These operations are carried out under the control of thesensor controller 80. The surrounding area sensor 70 corresponds to acombination of the road surface sensing device and the current locationverification device. The infrared cameras 73 and 73 are shared by bothdevices, so that the inner space of the robot R decreases. Thesurrounding area sensor 70 is connected to the controller 40, and it mayacquire self-location data from the gyro-sensor SR1 or GPS receiver SR2.

Referring to FIG. 3, the infrared cameras 73 and 73 are arrangedhorizontally on the front of the body R4 at its waist height in thisembodiment. The laser device 71 is located in the middle of the infraredcameras 73 and 73. The LED device 72 is placed around one (left one inFIG. 3) of the infrared cameras 73 and 73. As described above, the laserdevice 71, infrared LED device 72 and infrared cameras 73 and 73 areattached to the front of the body R4 at its waist height. This can beeffective to isolate these components from the vibration of the robot Ror from the interference of the arms R2 or legs R3, which wouldotherwise be experienced when attached to other portions of the body R4.

[Laser device]

The laser device 71 outputs slit light. This device, which is connectedto an actuator (not shown) for changing its light direction, isconfigured to irradiate the road surface, that is, the detection areawith radial slit light. The slit light irradiated on an object, such asthe road surface, forms bright lines. The laser device 71 is connectedto a sensor controller 80 (switch determination unit 82) (describedlater), and it turns on/off the slit light in response to an instructionfrom the sensor controller 80.

[LED Device]

The LED device 72 radiates infrared rays to the detection area. In thisembodiment, the LED device 72 is made up of multiple LEDs arrangedaround the left infrared camera 73, as shown in FIG. 3. The rays fromthe LED device 72 are to be reflected by the marks M. The LED device 72is connected to the sensor controller 80 (switch determination unit 82)(described later), and it turns on/off the infrared rays in response toan instruction from the sensor controller 80.

[Infrared Camera]

The infrared cameras 73 and 73 pick up images of objects in a digitalformat, and they may be a CCD infrared camera. As shown in FIG. 3, theinfrared cameras 73 and 73 are arranged horizontally on the front of thebody R4 at its waist height. The infrared cameras 73 and 73 output thecaptured images to the sensor controller 80.

The image produced by shooting the slit light on a detection area withthe infrared cameras 73 and 73 contains bright lines. Thereinafter, thisimage is called “slit light image”. Based on the bright lines, a lengthbetween the robot R and the shot object are estimated by employing aspecific method such as the light section method. The slit lights areshot by the dual infrared cameras 73 and 73, whereby the road surface isdetected in 3D dimensions. This is how the detailed geometry of the roadsurface can be recognized.

The image generated by shooting the infrared rays on a detection areawith the infrared camera 73 contains marks M. Thereinafter, this imageis called “infrared image”. As shown in FIG. 3, the infrared cameras 73and 73 are fixed to the waist of body R4 of the robot R at apredetermined angle. Accordingly, a relative positional relation betweenthe marks M and the infrared camera 73, that is, between the marks M andthe robot R is estimated based on where the marks M are positioned onthe image. The infrared image does not need to be captured by bothinfrared cameras 73 and 73. In this embodiment, only the left infraredcamera 73 is used.

[Sensor Controller]

Next, a detailed description will be given below, of the sensorcontroller 80. Referring to FIG. 4, the sensor controller 80 includesthe map data storage unit 81, a switch determination unit 82, a roadsurface sensing unit 83, a mark sensing unit 84, a self-locationcalculation unit 85, and a self-location correction unit 86.

[Map Data Storage Unit]

The map data storage unit 81 stores map data on the active area wherethe robot R moves around, and it may be a random access memory (RAM),read only memory (ROM) or hard disk. The map data contains position dataand mark-formed region data. The position data indicates where theindividual marks M are placed on the active area, while the mark-formedregion data indicates data generated by adding a predetermined width tothe position data. The map data storage unit 81 outputs the stored mapdata to the switch determination unit 82 and self-location calculationunit 85.

[Switch Determination Unit]

The switch determination unit 82 determines whether or not theself-location of the robot R is within the mark-formed region bycomparing the mark-formed region data (in the map data received from themap data storage unit 81) and self-location data (received from thegyro-sensor SR1 or GPS receiver SR2 via the controller 40). The switchdetermination unit 82, which is connected to the laser device 71 and LEDdevice 72, is configured to send an active or stop instruction to bothdevices.

If the self-location is determined to be out of the mark-formed region,then switch determination unit 82 sends an active instruction to thelaser device 71 as well as the stop instruction to the LED device 72.Otherwise, if the self-location is determined to be within themark-formed region, then switch determination unit 82 outputs a stopinstruction to the laser device 71 as well as an active instruction tothe LED device 72.

[Road Surface Sensing Unit]

The road surface sensing unit 83 detects the conditions of the roadsurface by analyzing the slit light image having been captured by theinfrared cameras 73 and 73. Specifically, it determines a distancebetween the area on the road surface irradiated with the slit light andboth the infrared cameras 73 and 73, by employing the light sectionmethod. The slit light is irradiated on the front area of the road inthe direction where the robot R moves. Therefore, the robot R realizesthe geometry of the road in the moving direction. The road surfacesensing unit 83 outputs the information on the conditions of the roadsurface to the controller 40.

[Mark Sensing Unit]

The mark sensing unit 84 analyzes the infrared image having beencaptured by the infrared camera 73 in order to detect the marks.

The unit 84 may monitor the rays outputted from the LED device 72selectively through a band pass filter. This filter has a cut-offfrequency which is nearly equal to the center frequency of rays from theLED device 72. This enables the rays of unwanted frequencies to be cut,so that the mark sensing unit 84 is isolated from disturbance light.

Furthermore, the mark sensing unit 84 measures individual distances ofthree points making up the mark M, and a distance between the pair ofmarks M (see FIG. 1). If the measured distances fall withinpredetermined lengths, then the unit 84 determines that the marks M arepresent. In this way, the mark sensing unit 84 resists disturbance lightsuch as rays reflected by objects other than the marks M.

[Self-location Calculation unit]

The self-location calculation unit 85 determines a relative positionalrelation between the marks M and the robot R, based on the position orcoordinates of the captured marks M on the infrared image.

The infrared cameras 73 and 73 are fixed to the waist of the robot R ata predetermined angle. Accordingly, it is possible to analyze where themarks M are positioned on the infrared image, that is, which pixels ofthe infrared image the marks M are positioned on. This makes it possibleto determine the relative positional relation between the robot R andthe marks M. Moreover, the self-location calculation unit 85 cancalculate how much the robot R is inclined with respect to a straightline coupling the two marks. Consequently, the self-location calculationunit 85 calculates precise self location of the robot R, based on thecoordinates of the marks M and the relative positional relation betweenthe marks M and the robot R. The unit 85 outputs the self location ofthe robot R to the self-location correction unit 86.

[Self-location Correction Unit]

The self-location correction unit 86 corrects the self-location of therobot R, based on the position data of the marks M that has beendetected by the mark sensing unit 84.

In this embodiment, the self-location correction unit 86 compares thetwo self-locations: one is determined by the self-location calculationunit 85 (first self-location); and the other acquired from thegyro-sensor SR1 or GPS receiver SR2 (second self-location). Then, ifthese locations differ from each other, then the unit 85 employs thesecond self-location, based on the premise that the first self-locationis more correct than the second one. The corrected self-location data isdelivered to the controller 40. As a result, errors made by theautonomous movement are eliminated, thus allowing the robot R to controlits movement surely and precisely.

Note that the way how the self-location correction unit 86 corrects theself-location is not limited thereto. Alternatively, the autonomousmovement controller 50 may adjust the location or orientation of therobot R in such a way that the marks M are positioned on a specificregion of the infrared image.

<Control Process of Mobile Robot>

Now, a detailed description will be given below, of how to control therobot R, more specifically, how to switch between the slit lightirradiation and the infrared irradiation, with reference to FIG. 5.

(Step 1)

First, the robot R acquires self-location data through the self-locationrecognition unit such as the gyro-sensor SR1 or GPS receiver SR2.Following this, the robot R realizes its current location from theself-location data, and then, outputs the data to the switchdetermination unit 82 through the controller 40.

(Step 2)

The switch determination unit 82 acquires map data containing theposition data on marks M from the map data storage unit 81.

(Step 3)

The switch determination unit 82 compares the self-location of the robotR and the mark-formed region of the marks M, thereby determining whetheror not the self-location is positioned within the mark-formed region.Specifically, the area which is located at less than a predetermineddistance away from the marks M is set as the mark-formed region of themarks M beforehand. Furthermore, this region is stored in the map datastorage unit 81.

Note that the way to determine the mark-formed region is not limitedthereto. Alternatively, the switch determination unit 82 may calculatethe distance between the self-location and the marks M, and then,determines that the robot R stands within the mark-formed region if thecalculated distance is less than a predetermined threshold value. Upondetermination, the unit 82 may account for the moving direction of therobot R. In this case, if moving away from the marks M, then the robot Rdoes not detect the marks M. Hence, even if the distance between themarks M and the self-location of the robot R is less than the thresholdvalue, then switch determination unit 82 may determine that the robot Ris not within the mark-formed region.

(Step 4)

If the self-location is determined to be out of the mark-formed region(“No” at the step 3), then the switch determination unit 82 outputs anactive instruction to the laser device 71 as well as a stop instructionto the LED device 72. Upon receipt of the active instruction, the laserdevice 71 irradiates the detection area on the road with radial slitlight, as shown in FIG. 1A. In addition, upon receipt of the stopinstruction, the LED device 72 stops radiating the rays.

(Step 5)

As soon as the laser device 71 outputs the slit light, the infraredcameras 73 and 73 pick up images of a detection area irradiated by theslit light, thereby obtaining slit light images. Subsequently, thecameras 73 and 73 output the slit light images to the road surfacesensing unit 83.

(Step 6)

The road surface sensing unit 83 analyzes the slit light images with thelight section method, thereby producing the geometry of the roadsurface. Thus, the unit 83 detects the road surface. Following this, theunit 83 outputs data on the geometry to the controller 40.

(Step 7)

The controller 40 compare the geometry of the road surface stored in themap data and that received from the road surface sensing unit 83.Subsequently, the controller 40 determines whether both geometries areidentical or not. If they are identical or the difference thereof fallswithin an allowable range (“No” at the step 7), then the controller 40determines there is not any obstacle. Subsequently, the process returnsto the step 1 and the robot R re-starts sensing its surrounding area.

(Step 8)

Otherwise, if the geometries differ or the difference exceeds theallowable range (“Yes” at the step 7), then the controller 40 determinesthat an obstacle is present. Following this, the controller 40 sends aninstruction for avoiding the obstacle to the autonomous movementcontroller 50. Specifically, this instruction allows the robot R to passthrough a different road or to remove the obstacle from the road.

It is assumed that there is no obstacle on the road but step heights areformed thereon. In this case, the controller 40 manipulates the legs R3or arms R2 of the robot R by not using the map data but the geometrydata sensed by the road surface sensing unit 83. This results in themore precise control of the robot R.

Next, the process at the step 3 will be described again.

(Step 9)

If the self-location of the robot R is within the mark-formed region ofthe mark M (“Yes” at the step 3), then the switch determination unit 82sends an active instruction to the LED device 72 as well as a stopinstruction to the laser device 71. The LED device 72 irradiates thedetection area on the road with infrared rays, in response to the activeinstruction (see FIG. 1B). The laser device 71 stops outputting the slitlight, in response to the stop instruction.

(Step 10)

As soon as the LED device 72 irradiates the mark-formed region with theinfrared rays, the infrared camera 73 picks up the images of thedetection area, thereby producing an infrared image. Since the marks Mmade of a reflecting material are provided on the detection area, theinfrared image contains the marks M. The infrared camera 73 outputs theinfrared image to the mark sensing unit 84.

(Step 11)

Upon receipt of the infrared image, the mark sensing unit 84 extractsthe marks M from the image through a band pass filter. This makes itpossible to realize which the pixel of the image the marks M arepositioned on.

(Step 12)

The self-location calculation unit 85 determines where the currentlocation of the robot R is, based on which portion of the infrared imagethe marks M are positioned on. Specifically, the self-locationcalculation unit 85 calculates the relative distance and angle betweenthe marks M and the robot R. Subsequently, the unit 85 executes anarithmetic process on the position data of the marks M read from the mapdata storage unit 81 by using the relative distance and the positiondata. Finally, the self-location of the robot R is determined. Due tothe fact that the position and angle of the infrared cameras 73 and 73are fixed, it is possible to determine the relative positional relationbetween the robot R and the marks M, based on which portion of theinfrared image the marks M are positioned on. In addition, since twomarks M make a pair, the relative angle between the marks M and therobot R can be determined. As a result, the orientation of the robot Ris also corrected.

When the robot R moves, the height and angle of the infrared cameras 73and 73 may be varied. However, the controller 40 can always monitor thepose of the robot R, based on the control data from the autonomousmovement controller 50. Furthermore, the controller 40 estimates thedistance between the cameras of the robot R in the basic pose and in thepresent pose. Finally, the controller 3 determines the precise heightand angle of the infrared cameras 73 and 73 by using the estimateddistance. Specifically, the height and angle of the infrared cameras 73and 73 can be compensated by using a specific data called “bendingmodel”. This data is related to a relation between the pose of the robotR and both the height and angle of the infrared cameras 73 and 73, andit is obtained beforehand by measurement, simulations, etc.

The self-location data of the robot R is outputted to the self-locationcorrection unit 86.

(Step 13)

The self-location correction unit 86 compares the two self-locations:one is determined by the self-location calculation unit 85 (firstlocation); and the other is received from the gyro-sensor SR1 or GPSreceiver SR2 (second location). If both self-locations are identical orthe difference thereof falls within an allowable range (“No” at the step13), the controller 40 does not correct the self-location. Then, theprocess returns to the step 1 and the robot R re-starts sensing itssurrounding area.

(Step 14)

Otherwise, if both locations differ or they are out of the allowablerange (“Yes” at the step 13), then the unit 85 employs the secondself-location, based on the premise that the first self-location is morecorrect than the second one. As a result, the errors made by theautonomous movement are eliminated, thus allowing the robot R to controlits movement surely and precisely.

With the above-described process, the robot R can switches between theslit light irradiation and the infrared irradiation appropriately.Consequently, it is possible to save a space inside the robot R byallowing the infrared cameras 73 and 73 to be in common use for both theslit light irradiation and the infrared irradiation. In addition, it ispossible to decrease the power consumption of the robot R by irradiatingthe infrared rays only as necessary.

As described above, the description of the present invention has beendescribed. However, the present invention is not limited thereto.

In this embodiment, the self-location calculation unit 85 determines thecurrent location, that is, the absolute coordinates of the robot R,based on the position data on the marks M. However, alternatively, itmay be possible to estimate the relative positional relation between themarks M and the robot R, based on the infrared image, and then, tocorrect the self-location of the robot R in such a way that theestimated relation meets a predetermined condition. In this case, thecoordinates of the robot R do not need to be determined, and this has anadvantage that the robot R does not need to stop at a specific location.

In this embodiment, the robot R is equipped with the map data storageunit 81. Alternatively, the unit 81 may be contained in a robotcontroller 3 separated from the robot R, and acquires the map datathrough the radio communicator 60 and the controller 40. In this case, acombination of the robot R, base station 1 and robot controller 3corresponds to the autonomous mobile robot.

Moreover, in addition to the map data storage unit 81, some or all ofthe switch determination unit 82, the road surface sensing unit 83, themark sensing unit 84, the self-location calculation unit 85, and theself-location correction unit 86 may be contained in the robotcontroller 3. In this case, it is preferable that the slit light imageor infrared image captured by the infrared cameras 73 and 73 be sent tothe robot controller 3 through the radio communicator 60.

In addition, three points make up a single mark M and two marks M make apair in this embodiment. However, the present invention is not limitedthereto. Alternatively, the shape of a mark may be a line or dottedline.

Furthermore, the above described components are not limited to specificconfigurations such as hardware, software or a combination thereof.These components may be implemented with any configurations as long astheir functions can be achieved.

From the aforementioned explanation, those skilled in the art ascertainthe essential characteristics of the present invention and can make thevarious modifications and variations to the present invention to adaptit to various usages and conditions without departing from the spiritand scope of the claims.

1. An autonomous mobile robot, comprising: a moving mechanism; anautonomous movement controller configured to control the movingmechanism; a self-location recognition unit configured to sense aself-location of the autonomous mobile robot within an active area; amap data storage unit configured to store a map data on locations ofmarks formed on the active area; a slit light device configured toirradiate a detection area with slit light; an infrared deviceconfigured to irradiate a detection area with infrared rays; a switchdetermination unit configured to compare a mark-formed region stored inthe map data storage unit and the self-location sensed by theself-location recognition unit, and then, configured to switch betweenthe slit light device and the infrared device, based on a result of thecomparison; a capture unit configured to capture an image of thedetection area irradiated by the slit light or infrared rays; a roadsurface sensing unit configured to detect conditions of a road surfaceby analyzing the captured image of the detection area being irradiatedwith the slit light; and a mark sensing unit configured to detect marksby analyzing the captured image of the detection area being irradiatedwith the infrared rays, wherein the infrared device irradiates thedetection area upon the self-location being within the mark-formedregion, while the slit light device irradiates the detection area uponthe self-location being out of the mark-formed region.
 2. The autonomousmobile robot according to claim 1, further comprising a self-locationcorrection unit configured to correct the self-location, based onlocations of the marks detected by the mark sensing unit.
 3. Theautonomous mobile robot according to claim 2, wherein the movingmechanism comprises a legged moving mechanism.
 4. The autonomous mobilerobot according to claim 2, wherein the slit light device, the infrareddevice and the capture unit are attached to a front body of theautonomous mobile robot at its waist height.
 5. The autonomous mobilerobot according to claim 2, wherein the capture unit is shared by boththe slit light device and the infrared device.
 6. The autonomous mobilerobot according to claim 1, further comprising a base station and arobot controller, the robot controller comprising the map data storageunit.
 7. The autonomous mobile robot according to claim 1, wherein themoving mechanism comprises a legged moving mechanism.
 8. The autonomousmobile robot according to claim 1, wherein the slit light device, theinfrared device and the capture unit are attached to a front body of theautonomous mobile robot at its waist height.
 9. The autonomous mobilerobot according to claim 1, wherein the capture unit is shared by boththe slit light device and the infrared device.
 10. A process forcontrolling an autonomous mobile robot, comprising: sensing aself-location of the autonomous mobile robot within an active area;acquiring a map data on locations of marks formed on the active area;comparing the self-location and a mark-formed region being acquired fromthe map data; and switching between slit light and infrared rays, basedon a result of the comparison, so that a detection area is irradiated,wherein the slit light and the infrared rays are switched in such a waythat the detection area is irradiated by the infrared rays upon theself-location being within the mark-formed region, while the detectionarea is irradiated by the slit light upon the self-location being out ofthe mark-formed region.